Under the continuing support of this project, we have established many of the molecular parameters describing HSV gene expression during the productive replication cycle and during latent infection. DNA sequence and RNA transcription analysis have allowed identification of specific functional elements throughout the genome. More recently, the molecular mechanisms and DNA sequence elements involved in controlling the expression of individual viral genes and the basis for their temporal control are being extensively analyzed. Such work involves both the defined mutagenesis of DNA sequence elements controlling individual viral genes, and the generation of recombinant viruses which Contain such mutated elements for the study of their function. The question of how virus mediated regulatory processes interact with precisely characterized viral promoters and the identification of putative virus-specific cis- acting promoter elements is of central importance in modeling HSV transcriptional regulation. A major goal of the project is the molecular description of the mechanism by which HSV can operate to optimize expression from promoters of differing functional architecture at different stages of infection. This will require identification of local, regional, and global factors influencing the interaction between the viral genome and the cell. Experimentally, the project has the following goals: l) Full characterization of the functional architecture in recombinant viruses of viral promoters which serve as good representatives of their particular kinetic class. 2) Evaluation of the role of promoter location and template accessibility within the viral genome in defining levels of express ion during periods of optimal and sub-optimal expression. 3) Initiation of preliminary immuno-cytochemical analysis of the changes in the cellular transcriptional milieu which leads to changes in transcription patterns during productive infection. 4) Investigation of the biological manifestations of specific promoter structure and kinetic class in terms of possible tissue specific cis- acting elements which may function during reactivation or under conditions of restricted viral replication.